by Sally Colby
If you’re working on the farm outside in winter and feel cold, chances are you can do something about it. What about the newborn calf?
Dr. Jerry Bertoldo, DVM and Regional Specialist with Cornell Cooperative Extension, says the biggest challenge in keeping young calves warm is their relatively small body mass, which leads to rapid heat loss.
“As temperature goes down, we get beyond the thermal neutral zone where they don’t need extra energy to keep warm,” said Bertoldo. “We dilute some of the needs they have for maintenance and growth, and it goes to keeping them warm.” Calves that would normally grow well in summer have more trouble in winter due to this diversion of energy.
Another challenge is the newborn calf’s lack of fat reserves. “The brown fat that newborns have is not plentiful,” said Bertoldo. “Maybe 18 hours at most when weather is warm, but when temperatures are cold, and before calves get anything to eat, that brown fat will only last a few hours. It’s really important to give that first feeding of colostrum early.”
One strategy to help young calves stay warm in winter is more frequent feeding, sometimes three times a day. However, since very few calves are fed 12 hours apart, it might be difficult to add a feeding. A third feeding in the middle of the day isn’t always ideal because the calf might still be full from the morning feeding. If the farm has adequate staff, perhaps someone pushing feed at night can provide a third feeding for very young calves.
Some farmers who use milk replacer add extra powder during cold weather, but Bertoldo says this practice can be problematic. “If you increase the solids concentration in the milk replacer and get much over 15 percent, you can run into issues, particularly if you have hard water,” he explained. “When you make 17 to 18 percent solids milk replacer, you’re concentrating some of the salts, and if you add hard water (that contains iron and sulfur) on top of that, it plays havoc with the calf’s guts. Clostridial bloats and enteritis result in quick deaths so it’s better to feed more often rather than more concentrated.”
Although offering starter feed earlier might seem like a good concept for cold weather, Bertoldo says it isn’t a good idea because the protein in starters is plant based and calves don’t have the ability to digest plant protein until they’re about two and one half weeks of age. “Calves (and cows) lack the starch-digesting enzyme amylase,” he said. “Ruminants digest starch in the rumen once the rumen bugs are established. We don’t need to push starter intake in calves until their digestion changes at about two to two and one half weeks of age.” Bertoldo says it’s worth offering starter to calves approaching that age to acquaint them with it, but it’s unrealistic to expect calves to consume enough to make a significant nutritional difference.
Cold weather water feeding can be problematic but it’s essential that calves receive one to two gallons of clean water daily, depending on age. Water should be about 80 degrees F and offered within an hour of milk or milk replacer. Bertoldo cautions that whole milk fed calves shouldn’t be offered water immediately after milk feeding because the milk requires time to curdle in the abomasum.
The calf’s environment and air ventilation is critical at any time of year, but winter brings unique challenges. “It doesn’t require much wind movement to be considered a draft on younger calves (under three weeks),” said Bertoldo. “In dry conditions and under 50 degrees F, a breeze that’s over 1 mph is considered a draft. As they get a little older, they can take more air movement.”
A draft-free environment is essential, and hutches are a good option if they’re well-bedded and open to the south. For inside housing with wire or panel pens, air movement should be adequate to provide good ventilation. Studies have shown that two-row barns ventilate naturally better than four-row barns. “In four-row barns, the outside rows do fairly well,” said Bertoldo. “The inside rows not so well. Calves don’t make enough heat for ridge vents to do any good, but anything over 40’ wide is tough to naturally ventilate. If you’re on a hill and prevailing wind is out of the west and you’re always guaranteed a breeze, the calves on the west side are going to be half-frozen by the time the calves on the east side get some decent air.”
An important aspect of ventilation is the presence of ammonia. “Ammonia is very irritating to the trachea and bronchi,” said Bertoldo. “If you can smell ammonia, there’s too much.”
Wet conditions and mud are winter challenges for calves. Mud or dirty bedding flattens the hair coat and reduces the insulating properties, which can result in chilling. Straw bedding insulates better than sawdust, and should be 4” to 6” deep to provide adequate warmth. The nesting score developed by Dr. Ken Nordlund at the University of Wisconsin is a good gauge of whether the calf has adequate bedding in cold weather.
A nesting score of 1 means that the calf’s legs are visible when the calf is lying down, and indicates insufficient bedding. With a score of 2, the calf’s legs are partially visible when the calf is lying down. A score of 3 is ideal for winter — the calf’s legs are not visible when calf is lying down. Calf jackets provide a significant amount of degree difference; potentially as much as 10 to 15 degrees. Jackets are usually removed when the calf outgrows the jacket, and should be washed between calves.
Disinfectants should be an important part of hygiene in winter, whether for hutches or concrete floors in a barn. “You need to remove dirt and organic matter,” said Bertoldo, adding that it’s important to read and follow product labels. “If you don’t get the dirt and crud off, you aren’t going to sanitize below that stuff. Another thing to remember is that disinfectants don’t kill everything — there are always survivors. What we’re doing is cutting the risk.” Factors such as temperature, concentration, water pH, water hardness and excessive organic matter can affect disinfectants.
Calf health status involves three factors that work together: pathogen exposure, environmental stress and nutrition. “A lot of calves’ stress is related to the environment,” said Bertoldo. “Wet, cold, a draft, how rough we handle them, how isolated they are (can’t see other calves). Nutrition is really important in young calves because it feeds the immune system.” Bertoldo added that the most common causes of calf death, whether the death was due to respiratory illness or scours, are dehydration and undernutrition.
The impact of dystocia on young calves should not be overlooked. Physical trauma, low blood oxygen levels and hypothermia are common in calves that have been pulled. “Any calf, any time of year, will actually cool down after a difficult calving,” said Bertoldo. “If the core body temperature goes down for around an hour, there’s a serious impact on how the calf responds to disease challenges. The immune system doesn’t work well and the absorption of antibodies from colostrum isn’t good.” Bertoldo added that when calves are born in winter, especially at night, there’s a higher risk of shivering or lying out in a draft for extended period of time.